I have two Ford pickups. One is an '89 F-250 Lariat 4X4, auto with a
new 460 engine.

The other truck is a '90 F-150 Lariat 4X4 auto w/OD, and a well worn
302. Both are now "work" trucks and are driven every day.

The F-150 still runs well, even with all the miles on it, and it
gets EXCELLENT, (or, at least, I'm satisfied with it) gas mileage.
Unfortunately, the F-250 doesn't.

I didn't realize it when I purchased it last fall, but, I think it
must have been a specially ordered pick up because it has an extremely
low-geared rear end, and NO overdrive.

At 55, you can hear that big 460 whine, like it's stuck in a lower
gear, but, according to several reliable mechanics, it isn't. The truck
was obviously built to work off-road more than on. Hence, the low
gearing.

My 1st question is, does anybody know if I can get a higher geared
rear end for it?
The second, will I have to change the ratio in the front axle as well?
Won't that affect it's 4-WD capabilities if I don't? Thanks in advance!

Joe

EYEWOOD2 (AT) webtv (DOT) net (Joe Hartley) started a controversy when he said in
news:5102-3EFE345D-8 (AT) storefull-2175 (DOT) public.lawson.webtv.net:

Yes, the ring and pinion can be change to a numerically lower gear(lower
ratio). By the way you describe it, I would guess the current gear to be
around 4.10:1 and with that motor you probably don't need anything higher
than a 3.55:1. Then again, I suppose you could just install a set of
monster truck tires, that will effect your final drive ratio too.

Yes, you will have to match the ratios in both axles.


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I've changed rear ends four times. I like this last one, I think I'll keep her


Sorry, just had to.

I actually had a 4 wheel drive truck with different geared axles. It had a
3.92 Dana 44 front and a 9-inch Ford rear. Now, they don't make a 3.92
9-inch Ford, they make a 3.90. So that was considered "close enough" when it
was built. When I got it, the rear was a 3.70. Somebody had changed it. The
problem gets worse by degrees as the speeds differ more.

Anyway, if you have this situation the wheels are going to turn different
speeds in 4 wheel drive and there's just no way around it. It's an
overstatement to say they have to be the same. It would be really bad on
pavement (you'd break something), but if you're knee-deep in mud you
wouldn't even notice it. It'll be dangerous in the snow because you'll have
one back tire spinning all the time and it'll be easier to break loose. Some
judgement is called for, but in most cases you'd want to change them both.

"Joe Hartley" <EYEWOOD2 (AT) webtv (DOT) net> wrote

My cousin worked in a Montgomery Wards auto service thing 20 years ago. One
day this woman drives in and says "my Husband stuck his finger in my rear
end last night and it was dry as a chip". You can imagine that they just
about hyperventilated laughing, and she was embarrased and didn't think it
was funny.

Instead of changing differentials you might consider installing larger tires
if they will fit. This will effectively reduce your gear ratio though you
won't get as good fuel mileage as if you had just done the gears. Worth
considering though.

Andrew

"Joe Hartley" <EYEWOOD2 (AT) webtv (DOT) net> wrote